feat: add xml marshal for Int type (#365)

Co-authored-by: Clyde <clyde.m@nodereal.io>

math/int.go

@@ -3,6 +3,7 @@ package math
 import (
 	"encoding"
 	"encoding/json"
+	"encoding/xml"
 	"fmt"
 	"math/big"
 	"strings"
@@ -327,6 +328,20 @@ func (i Int) String() string {
 	return i.i.String()
 }
 
+// MarshalXML defines custom encoding for xml Marshaler
+func (i Int) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	return e.EncodeElement(i.String(), start)
+}
+
+// UnmarshalXML defines custom decoding for xml Marshaler
+func (i *Int) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	var s string
+	if err := d.DecodeElement(&s, &start); err != nil {
+		return err
+	}
+	return i.Unmarshal([]byte(s))
+}
+
 // MarshalJSON defines custom encoding scheme
 func (i Int) MarshalJSON() ([]byte, error) {
 	if i.i == nil { // Necessary since default Uint initialization has i.i as nil

math/int_test.go

@@ -2,6 +2,7 @@ package math_test
 
 import (
 	"encoding/json"
+	"encoding/xml"
 	"fmt"
 	"math/big"
 	"math/rand"
@@ -396,6 +397,14 @@ func (s *intTestSuite) TestIntEq() {
 	s.Require().False(resp)
 }
 
+func (s *intTestSuite) TestIntXmlMarshalRoundTrip() {
+	u1 := math.NewInt(256)
+	marshalResult, _ := xml.Marshal(u1)
+	u2 := math.Int{}
+	xml.Unmarshal(marshalResult, &u2)
+	s.Require().Equal(u1, u2)
+}
+
 func TestRoundTripMarshalToInt(t *testing.T) {
 	values := []int64{
 		0,